Surprised you've not had any US ones posted yet so here's one for NZ to get things going.
It’s a circular route so can be done in either direction from any point. One of favourite “I’m just popping out for some milk” trips;-)
This is a variation on the Twin Passes route popular with Christchurch riders but uses more back roads. There’s some gravel but nothing difficult and it can be avoided. If going from Christchurch I recommend starting and finishing in Rangiora as that will give you more interesting roads ride.
From Rangiora head north towards Loburn. Turn left onto Hodgsons Road, follow this all the way into Oxford. You often have this road all to yourself and even the longer straights at the start are fun to ride. As it beings to skirt the Alps the road begins to curve around more and there’s some nice technical bends that can be joy to ride. If riding in winter be careful of the section by the alps because parts of the road are often in shade and so can be icy even in the middle of the day.
When you get to Oxford turn left onto SH72. You can stick on this road, alternatively you can take a little detour again onto Woodside Road. This leads you on a nice little back road detour, the trick is to just follow the tarmac at each junction as all the other roads are gravel. Just be careful of the Monseys/Island Road junction as that’s a tight turn that appears suddenly. Eventually you’ll join rejoin SH72 just before Waimakariri Gorge.
If you’re behind anything at then pull into the layby just past the bridge to let the road clear. That way you can fully enjoy the tight switchbacks going up the other side of the gorge.
At Springfield turn right onto SH73 heading for Arthurs Pass and through some of the most spectacular and ever-changing scenery in the South Island. After 131km turning right onto Lake Brunner Road. Now you can stick on this this road for 70km until you get to SH7 and turn right.
But if you don’t mind a bit of gravel then take the right (it’s actually straight) just before Rotomanu onto Bell Hill Road following the signs for Nelson Creek and then finally turning left onto SH7.
At Reefton follow SH7 towards Springs Junction, towards Lewis Pass right through to Hurunui. If you want to relax for a bit then turn off SH7 to the hot springs at Hamner Springs. Lewis Pass has a more stark beauty to it than Arthurs Pass, and there are parts of the road where you wouldn't be surprised if a dinosaur stuck its head out from between the moss covered trees and ferns - well maybe a bit
Another gravel detour at this point is just a couple of 2km past Hurunui where you take the right-hand turning marked Hawarden. In Hawarden go straight across the mini-roundabout onto Allandale Road, then at Masons Flat Engineering take the second right onto Heathstock Road. The road begins to follow the Waipara River Gorge and offers some great views.
You will eventually hit tarmac again, follow the signs for Amberley through two right hand turns. Look out for Broomfield school on the right, about 1.5 km past this the road bends sharply to the left, take the right-hand turning there and then left onto Reserve Road. Follow this back to Rangiora.
Total distance, around 570km to 600km (354 to 373 miles) depending on which side road detours you take.